Rapid lead and cadmium adsorption from aqueous solutions using modified chitosan with citric acid before analysis by flame atomic absorption spectrometry

In this research, a modified chitosan (NH2-CS-COOH) with natural citric acid was used for the adsorption and removal of lead (Pb2+) and cadmium (Cd2+) ions in the liquid phase. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) were achieved using the sorbent. The concentrations of Cd(II) and Pb(II) ions were determined by flame atomic absorption spectrometry (F-AAS). Parameters in batch adsorption were studied, including adsorbent amount, contact time, concentration, and temperature. Optimized conditions were obtained for lead and cadmium using 10 mg and 20 mg of adsorbent (NH2-Cs-COOH), respectively. Also, the contact times of 105 min for lead and 120 min for cadmium were obtained with an initial concentration of 10 mg L-1. The data showed a better agreement with the Langmuir model, indicating maximum adsorption capacities (qₘₐₓ) of 3.18 mg g-1 and (qₘₐₓ) of 2.07 mg g-1 for lead and cadmium ions, respectively. Thermodynamic studies confirmed that the process is exothermic with negative ΔG° values. The results demonstrate that the adsorbent is highly effective for removing heavy metals from polluted water.